Viscometers, which are devices for measuring viscosity of materials, operate according to known principles and standards. One such viscometer is described in Cannon et al Pat. No. 3,277,694, assigned to the Cannon Instrument Company of State College, Penna.
Of particular interest to the present invention is a commercially available viscometer, a cold cranking simulator provided under the designation CCS by the Cannon Instrument Co. Such a viscometer is used in the petroleum industry for measurement of oil viscosity in accordance with a standardized test procedure D2602 established by the American Society for Testing and Materials (ASTM).
In a typical application, oil samples are provided to a measurement station using a viscometer such as the CCS, where appropriate measurements are conducted under the established standards, to determine a proper viscosity grading for the petroleum product. The measurement procedure requires manual injection of the sample to a sample chamber, passing of appropriate temperature fluids in the vicinity of the sample for temperature control of the sample, and measurement of the sample viscosity at the appropriate temperature. Cleansing of the measurement chamber between samples is required in order to avoid contamination of successive samples, and separate cleansing fluids are used for that purpose.
However, the above described prior art procedure is labor intensive and thus expensive. Further, because of manual supply of the samples to the viscometer, an opportunity exists for errors to occur. Particularly, an operator may provide the wrong sample for measurement, or provide a single grade base stock for a multigrade product, so that mislabeling of the product may thus result.
Moreover, for a system using a cleansing solution of the measurement chamber there must be provided adequate disposal of the solvent. Thus an environmental problem is caused by such a device.
Additionally, manual operation of the viscometer is time consumptive and may require several attempts to complete a single measurement.
In order to overcome some of the above described difficulties, it has been proposed to provide an automated cold cranking simulator, requiring a reduced amount of manual intervention. In such a prior art simulator, a microprocessor controlled programmable current source has been used to minimize operator intervention. Similarly, a microprocessor has been used to maintain appropriate temperatures for the coolant fluids for both hot and cold baths of the simulator.
While such a prior art cold cranking simulator overcomes some of the difficulties of the prior art, a problem of still greater significance remains without solution.
A significant difficulty of the prior art is the fact that continuous, unattended and automated monitoring of a product of a blending plant has heretofore been impossible. Even in the improved viscosity measurement devices, manual loading is required of a sample changer carouse. An operator is required to load syringes with both test samples and reference samples. Thus, after conducting the measurements the syringes used in the sample delivering carousel must either be cleaned or discarded. Moreover a rotatable magazine, or carousel, as used in the prior art to provide a plurality of syringes to the viscometer, is susceptible to jamming.
Accordingly, it is seen that continuous, unattended monitoring is not provided even by he improved prior art system. Moreover, operator error may still occur in providing the wrong samples for measurement, or in providing the wrong reference sample for comparison. Additionally, a further processing step is required to cleanse the syringes after the measurement, adding to the expense of operation of the device. Aternatively, if the syringes are discarded subsequent to measurement, still another expense must be incurred by the more recent systems.
Since cold cranking simulator viscosity is a primary indicator used for maintenance of quality control during bending of multigrade motor oils, repeated, unattended monitoring of this parameter, i.e., continuous nonitoring would provide a significant improvement of product quality assurance. The failure of the prior art to provide a continuous monitoring process for cold cranking viscosity thus adds to the degree of uncertainty in product viscosity and product reliability and to a decrease in quality control.
In a typical bending plant, CCS viscosity measurements are performed from ten to fifteen times per day to insure product quality. Thus much of the blended product is provided without viscosity data. However, in view of the labor intensive approaches of the prior art it has thus far been too difficult or expensive to increase the number of viscosity measurements.
As is known in the art, a viscosity improver (VI) is added to multi-grade motor oils in response to the viscosity measurements, thus providing an optimal formulation of multi-grade oils. However, since the polymers in a VI improver form deposits on engine parts and may adversely affect engine operation, it is desirable to add a minimum quantity of the VI to the oils and yet to add a sufficient quantity to attain the desired viscosity.
In order to achieve and maintain the desired balance, wherein enough VI is added to provide the required viscosity while holding engine deposits to a minimum, it is necessary for the bender to have continuous feedback of CCS viscosity data during blending.
Continuous monitoring of viscosity data is also quite helpful in avoidance of the wrong base stock in the bending process, such as use of Bright Stock instead of 100N for production of 5W-30 motor oil. Under a continuously monitored bending operation, provision of the wrong stock quickly results in viscosity readings which deviate from the expected values, thus alerting the blender to a quick correction of the error. There is accordingly a need in the prior art for automated, unattended and substantially continuous monitoring of CCS data for a bending process. Without such continuous, unattended, monitoring it is impossible to provide full automation of a blending, bottling or canning facility.